Aluminum and copper hot line clamps are used by electric utilities for mechanically and electrically joining one overhead line conductor to another or to a power transformer, lightning arrester, capacitor bank or other piece of electrical equipment.
One of the problems associated with the use of present day hot line clamps is that the conductor must be wire brushed prior to application of the clamp, to remove surface oxide. Surface oxide increases electrical resistance at the contact points. Should a hot line clamp be used on an old or insufficiently cleaned conductor, the clamp will overheat at the contact points under the current loading and may melt and drop the line. Overheating is caused by poor electrical contact due to the presence of surface oxide on the conductor. The thicker the oxide film the more the overheating and hence the more critical the problem.
Adding to the problem is the fact that the clamp is usually clamped on to at least one of the conductors by an eyebolt which is turned and tightened by a lineman with a long pole called a hotstick or shotgun. Torque applied to the eyebolt by a hotstick or shotgun is on the order of 16 to 20 pounds which in many cases is not enough to make a good contact. This increases the likelihood of failure even when only a relatively thin oxide film is present on the conductor.